U.S. patent application number 09/986686 was filed with the patent office on 2002-05-30 for recording apparatus for use with optical recording medium and method thereof.
This patent application is currently assigned to PIONEER CORPORATION. Invention is credited to Sakata, Haruyasu, Tanaka, Hiroyuki, Yoshida, Mitsuru.
Application Number | 20020064114 09/986686 |
Document ID | / |
Family ID | 18818397 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020064114 |
Kind Code |
A1 |
Sakata, Haruyasu ; et
al. |
May 30, 2002 |
Recording apparatus for use with optical recording medium and
method thereof
Abstract
An optical recording apparatus includes a light source driving
unit for driving a light source; an emitted light power detecting
unit for detecting an emitted light power; a temperature detecting
unit for detecting a temperature of the light source; a light power
control unit for adjusting a driving current of the light source
such that a change rate of an emitted light power detection value
fall within a predetermined range; and a detection value storing
unit for storing a driving current adjustment value in association
with a temperature detection value. The light power control unit
adjusts the driving current value of the light source based on an
stored detection value when the temperature detection value is
within a range of temperature detection values already stored in
the detection value storing unit.
Inventors: |
Sakata, Haruyasu;
(Tokorozawa-City, JP) ; Tanaka, Hiroyuki;
(Tokorozawa-City, JP) ; Yoshida, Mitsuru;
(Tokorozawa-City, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
PIONEER CORPORATION
|
Family ID: |
18818397 |
Appl. No.: |
09/986686 |
Filed: |
November 9, 2001 |
Current U.S.
Class: |
369/53.26 ;
G9B/7.099 |
Current CPC
Class: |
G11B 7/126 20130101 |
Class at
Publication: |
369/53.26 |
International
Class: |
G11B 007/125 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2000 |
JP |
2000-344148 |
Claims
What is claimed is:
1. An optical recording apparatus for performing recording by
irradiating a light beam emitted from a light source to a recording
medium, comprising: a light source driving portion for driving said
light source; an emitted light power detecting portion for
detecting an emitted light power from said light source; a
temperature detecting portion for detecting a temperature of said
light source; a light power control portion for adjusting a driving
current of said light source such that a change rate of an emitted
light power detection value from said emitted light power detecting
portion fall within a predetermined range; and a detection value
storing portion for storing a driving current adjustment value from
said light power control portion and a temperature detection value
from said temperature detecting portion in an associated manner,
wherein said light power control portion adjusts the driving
current value of said light source based on an stored detection
value in said detection value storing portion when the temperature
detection value is within a range of temperature detection values
already stored in said detection value storing portion.
2. An optical recording apparatus according to claim 1, further
comprising: a correction coefficient storing portion for storing a
correction coefficient for the driving current value corresponding
to the temperature of said light source in advance, wherein said
light power control portion adjusts the driving current value of
said light source by using the correction coefficient already
stored in said correction coefficient storing portion when the
driving current adjustment value corresponding to a current
temperature detection value is not stored in said detection value
storing portion.
3. An optical recording apparatus according to claim 1, wherein:
said light power control portion computes an interpolation value of
the stored detection value to adjust the driving current of said
light source based on the interpolation value.
4. An optical recording apparatus according to claim 1, further
comprising: a medium determining port ion for determining whether
the recording medium is newly loaded or not, wherein said detection
value storing portion updates the stored detection value with a new
detection value when said medium determining portion determines
that the recording medium is newly loaded.
5. An optical recording apparatus for performing recording by
irradiating a light beam emitted from a light source to a recording
medium, comprising: a light source driving portion for driving said
light source; an emitted light power detecting portion for
detecting an emitted light power from said light source; a
temperature detecting portion for detecting a temperature of said
light source; a light power control portion for adjusting a driving
current of said light source driving portion to maintain the
emitted light power from said light source substantially at a
predetermined value, and a detection value storing portion for
storing a driving current adjustment value from said light power
control portion and a temperature detection value from said
temperature detecting portion in an associated manner, wherein said
light power control portion adjusts the driving current value of
said light source based on an stored detection value in said
detection value storing portion when the temperature detection
value is within a range of temperature detection values already
stored in said detection value storing portion.
6. A recording method of an optical recording apparatus for
performing recording by irradiating a light beam emitted from a
light source to a recording medium, comprising: light source
driving step of driving said light source; emitted light power
detecting step of detecting an emitted light power from said light
source; temperature detecting step of detecting a temperature of
said light source; light power control step of adjusting a driving
current of said light source such that a change rate of an emitted
light power detection value in said emitted light power detecting
step fall within a predetermined range; and detection value storing
step of storing a driving current adjustment value in said light
power control step in association with a temperature detection
value obtained in said temperature detecting step, wherein said
light power control step adjusts the driving current of said light
source based on an stored detection value in said detection value
storing step when the temperature detection value is within a range
of temperature detection values already stored in said detection
value storing step.
7. A method according to claim 6, further comprising: correction
coefficient storing step of storing a correction coefficient for
the driving current value corresponding to the temperature of said
light source in advance, wherein said light power control step
adjusts the driving current of said light source by using the
correction coefficient already stored in said correction
coefficient storing step when the driving current adjustment value
corresponding to a current temperature detection value is not
stored in said detection value storing step.
8. A method according to claim 6, wherein: said light power control
step computes an interpolation value of the stored detection value
to adjust the driving current of said light source based on the
interpolation value.
9. A method according to claim 6 further comprising: medium
determining step of determining whether the recording medium is
newly loaded or not, wherein said detection value storing step
updates the stored detection value with a new detection value when
it is determined that the recording medium is newly loaded in said
medium determining step.
10. A recording method of an optical recording apparatus for
performing recording by irradiating a light beam emitted from a
light source to a recording medium, comprising: light source
driving step of driving said light source; emitted light power
detecting step of detecting an emitted light power from said light
source; temperature detecting step of detecting a temperature of
said light source; light power control step of adjusting a driving
current of said light source to maintain the emitted light power
from said light source substantially at a predetermined value, and
detection value storing step of storing a driving current
adjustment value in said light power control step in association
with a temperature detection value obtained in said temperature
detecting step, wherein said light power control step adjusts the
driving current of said light source based on an stored detection
value when the temperature detection value is within a range of
temperature detection values already stored in said detection value
storing step.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] The present invention relates to an apparatus and method for
performing recordation by irradiating a light beam to a recording
medium.
[0003] 2. Description of the related art
[0004] It is necessary to control an emission power of a light
source (laser diode or the like) to maintain a predetermined
constant value during recording operation in order to achieve a
satisfactory reproduction performance with a recording and/or
reproducing apparatus or an optical disc drive for use with a
recordable or rewritable optical disc, such as a DVD-R (Digital
Versatile Disc-Recordable), a CD-R (Compact Disc-Recordable), a
DVD-RW (DVD-Rewritable), and a CD-RW (CD-Rewritable).
[0005] Conventionally, the laser diode is driven by a driving
current which is servo-controlled so as to maintain light power at
a constant level when reading from an optical disc. When performing
recording, the driving current is added with a current necessary to
achieve a light power for recording while performing the servo
control. FIG. 1 shows power characteristics of the laser diode
which is dependent on the temperature of the laser diode. More
specifically, the drawing shows a relation of light power (L)
versus driving current (Id) in terms of the temperature of the
laser diode as a parameter. Light power of the laser diode
increases approximately linearly with respect to a driving current
when the driving current is larger than an oscillation threshold
value (Ith). As the temperature of the laser diode increases, the
oscillation threshold value increases while slope efficiency or
external differential quantum efficiency (.eta.d[W/A]) representing
a gradient of the characteristics curve decreases.
[0006] It is a problem in the above-described conventional driving
method of the laser diode that recording light power varies even
when the recording is performed intermittently because the external
differential quantum efficiency of the laser diode varies as the
temperature of the laser diode changes. It is another problem in
the conventional driving method that the individual differences
among laser diodes cause variations in light power during recording
operation, because the temperature dependence of the laser diode
characteristics varies from element to element.
OBJECT AND SUMMARY OF THE INVENTION
[0007] The present invention has been made to overcome the
above-described problems, and it is an object of the present
invention to provide an optical recording apparatus capable of
performing a light power control with high accuracy in a stable
manner even when performing the recording intermittently and
regardless of a length of intermittent time intervals, and a method
thereof.
[0008] To achieve the object, according to one aspect of the
present invention, there is provided an optical recording apparatus
for performing recording by irradiating a light beam emitted from a
light source to a recording medium, which comprises a light source
driving portion for driving the light source; an emitted light
power detecting portion for detecting an emitted light power from
the light source; a temperature detecting portion for detecting a
temperature of the light source; a light power control portion for
adjusting a driving current of the light source such that a change
rate of an emitted light power detection value from the emitted
light power detecting portion fall within a predetermined range;
and a detection value storing portion for storing a driving current
adjustment value from the light power control portion and a
temperature detection value from the temperature detecting portion
in an associated manner, wherein the light power control portion
adjusts the driving current value of the light source based on an
stored detection value in the detection value storing portion when
the temperature detection value is within a range of temperature
detection values already stored in the detection value storing
portion.
[0009] According to another aspect of the present invention, there
is provided a recording method of an optical recording apparatus
for performing recording by irradiating a light beam emitted from a
light source to a recording medium, which comprises light source
driving step of driving the light source; emitted light power
detecting step of detecting an emitted light power from the light
source; temperature detecting step of detecting a temperature of
the light source; light power control step of adjusting a driving
current of the light source such that a change rate of an emitted
light power detection value in the emitted light power detecting
step fall within a predetermined range; and detection value storing
step of storing a driving current adjustment value in the light
power control step and a temperature detection value obtained in
the temperature detecting step in an associated manner, wherein the
light power control step adjusts the driving current of the light
source based on an stored detection value in the detection value
storing step when the temperature detection value is within a range
of temperature detection values already stored in the detection
value storing step.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows temperature dependence of optical power
characteristics of a laser diode wherein a relation of light power
(L) versus a driving current (Id) is illustrated while using a
temperature as a parameter;
[0011] FIG. 2 is a block diagram illustrating a configuration of an
optical recording apparatus according to one embodiment of the
present invention;
[0012] FIG. 3 is a flowchart detailing an operation procedure of
the optical recording apparatus according to one embodiment of the
present invention when performing a light power control of the
laser diode during recording operation; and
[0013] FIG. 4 is a time chart showing one example of the light
power control operation of the laser diode when performing
intermittent recording.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The following description will describe one embodiment of
the present invention with reference to the accompanying drawings,
in which substantially equivalent components are labeled with like
reference numerals for simplicity of description.
[0015] FIG. 2 is a block diagram illustrating a configuration of an
optical recording apparatus 10 according to one embodiment of the
present invention. In the drawing, a laser diode 5 serving as a
light source is provided in an optical pick-up (not shown) and
emits a beam of laser light irradiated to an optical disc, such as
a DVD-R and a DVD-RW. Also, a light detector 7 (front monitor
detector: FMD) detects output power of laser light emitted from the
laser diode 5 (that is, front output light) to the optical disc. A
monitor current signal representing light power detected by the
front monitor detector 7 is converted to a voltage signal by a
current-to-voltage (I/V) converter 11 first, and then is converted
to a digital signal by an analog-to-digital (A/D) converter 13. A
front monitor signal S1 obtained by these conversions is supplied
to a controller 15.
[0016] A temperature detector 17 for detecting a temperature of the
laser diode 5 is provided in the vicinity of the laser diode 5 in
the optical pick-up. A detection signal from the temperature
detector 17 is supplied to an analog-to-digital (A/D) converter 19
and converted into a digital signal. A temperature detection signal
S2 obtained by the conversion is supplied to the controller 15.
[0017] The controller 15 determines a driving current of the laser
diode 5 based on the front monitor signal S1 and the temperature
detection signal S2 to send a laser-diode (LD) driving control
signal S3 specifying the driving current to an LD driver 21.
Alternatively, the controller 15 determines the driving current of
the laser diode 5 based on a content stored in a storage device 23
(hereinafter, referred to simply as a memory) including a ROM (Read
Only Memory) and a RAM (Random Access Memory) to send the LD
driving control signal S3 specifying the driving current to the LD
driver 21.
[0018] A power calibration circuit 25 finds optimal recording light
intensity by performing power calibration described below for an
optical disc loaded in the optical recording apparatus 10 under the
control of the controller 15. The result thus obtained is supplied
to the controller 15. A disc determination circuit 27 determines
whether an optical disc is loaded into (or removed from) the
optical recording apparatus 10 or not to send the determination
result to the controller 15.
[0019] With reference to the flowchart of FIG. 3 and the time chart
of FIG. 4, an operation of the above-described optical recording
apparatus 10 when performing the light power control of the laser
diode 5 during recording operation. The operation is performed
under the control of the controller 15.
[0020] The controller 15 determines whether a disc is replaced (or
newly loaded) in the optical recording apparatus 10 (Step S11). In
this instance, the controller 15 may identify the disc itself by
reading out information or the like recorded on the disc, or
determine the opening of a disc tray or the like. Upon determining
that the disc is neither replaced nor newly loaded, the controller
15 skips to Step S19 and beyond for further operation. On the other
hand, when it is determined that the disc is replaced or newly
loaded, the controller 15 proceeds to the following steps to find a
reference value for optimal recording light intensity and the
recording light power control.
[0021] Initially, the power calibration circuit 25 sends the
driving signal to the LD driver 21, so that trial recording on the
optical disc is performed by driving the laser diode 5. Herein,
trial data to be recorded depends on an information data recording
format of the optical disc, and for example, data having a pit
length of 3T to 11T (T: channel bit length) is used. Optimal light
power for the recording is found by performing the trial recording
as discussed above while changing light power (Step S12).
[0022] Subsequently, the controller 15 drives the laser diode 5 to
achieve the optimal light power. The front light power of the laser
diode 5 during recording operation is monitored by the front
monitor detector 7 to detect a reference monitor current (I.sub.mo)
(Step S13). The controller 15, then, starts the recording of
information data on the optical disc (Step S14). The controller 15
control such that a front monitor current (FM current: I.sub.m)
from the front monitor detector 7 is maintained at the reference
monitor current (I.sub.mo). The controller 15 may control the front
monitor current (I.sub.m) or the change rate of the current
(I.sub.m) so as to fall within a predetermined range. The
controller 15 stores temperature detection values and the
corresponding driving current values (Id) of the laser diode 5
during the control operation into a learning table in an associated
manner in the memory 23 as storage data (Step S15).
[0023] As an example of the above control operation, the light
power control of the laser diode 5 during intermittent recording is
shown in FIG. 4. In this example, 25.degree. C. is given as a
temperature corresponding to the intensity of the detection
temperature signal S2 at the start of the recording of the
information data, and the temperature increases gradually as the
recording proceeds. The light power of the laser diode 5 decreases
as the temperature increases ((i) in FIG. 4). When a change (i.e.,
a decrease, in this example) of the light power reaches a
predetermined ratio ((ii) in FIG. 4), the controller 15 changes
(i.e., increases) the driving current (Id) of the laser diode 5
((iii) in FIG. 4), thereby making an adjustment so that the front
monitor current (I.sub.m) of the front monitor detector 7 is
substantially equal to the reference monitor current (I.sub.mo)
((ii) in FIG. 4). The controller 15 stores the temperature
detection values and the corresponding driving current adjustment
values obtained during the control operation into the learning
table in a one-to-one correspondence.
[0024] The controller 15 determines whether the recording operation
is suspended or not (Step S16). When it is determined that the
recording operation is not suspended, control is returned to Step
S15, and the controller 15 adjusts the light power and stores the
data into the learning table again in the manner discussed above
while performing the information data recording.
[0025] When it is determined that the recording operation is
suspended in Step S16, the controller 15 further determines whether
the recording has finished or not (Step S17). Upon determining that
the recording has finished in this step, control exits this
sub-routine and returns to the main routine.
[0026] Upon determining otherwise, the controller 15 determines
whether the recording is resumed or not (Step S18). Upon
determining that the recording is not resumed, control returns to
Step S17 and repeats Steps S17 and S18.
[0027] Upon determining that the recording operation is resumed in
Step S18, the controller 15 obtains a current temperature detection
value from the temperature detector 17 (Step S19). Then, the
controller 15 determines whether the detection temperature data and
the corresponding driving current data are already stored in the
learning table (Step S20). Upon determining that the data are
already stored in the learning table, the controller 15 acquires
the driving current data corresponding to the detection temperature
data from the learning table (Step S21). Upon determining that the
learning table has no driving current data corresponding to the
detection temperature data in Step S20, the controller 15 computes
a driving current by using a correction coefficient in a
temperature correction table pre-stored in another region of the
memory 23 besides the learning table (Step S22). Herein, in a case
where it is determined that there is no change in temperature when
the recording was suspended, data at the time of suspension may be
used.
[0028] Then, the controller 15 drives the laser diode 5 with the
driving current value, and detects the reference monitor current
(I.sub.mo) (Step S23). Subsequently, the controller 15 starts the
recording of the information data on the optical disc (Step S24:
(iv) in FIG. 4). The controller 15 controls such that the front
monitor current (I.sub.m) of the front monitor detector 7 is
maintained at the reference monitor current (I.sub.mo). Also, the
controller 15 stores the detection temperature data and the driving
current (Id) data of the laser diode 5 during the control operation
into the learning table in the memory 23, or updates the learning
table with the data (Step S25).
[0029] The controller 15 determines whether the recording operation
is suspended or not (Step S26). Upon determining that the recording
is not suspended, the controller 15 returns to Step S25, and
adjusts the light power and stores the data into the learning table
again in the manner discussed above while performing the
information data recording.
[0030] Upon determining that the recording operation is suspended
in Step S26, the controller 15 returns to Step S17, and repeats
Step S17 and beyond. By following the procedure discussed as above,
the light power control of the laser diode 5 during recording
operation is performed.
[0031] The embodiment is described above for a case where the
driving current value of the laser diode 5 is adjusted by using the
stored detection temperature data and the driving current (Id) data
themselves. It should be appreciated, however, that it may be
arranged in such a manner that an interpolation value of the stored
detection temperature data and driving current (Id) data is
computed, so that the driving current value of the laser diode 5 is
adjusted based on the interpolation value.
[0032] As has been described in detail, the temperature of the
laser diode 5 and the front output light from the laser diode 5 are
monitored, and the driving current during recording is adjusted
such that the monitor current value (that is, emission light power)
is within a predetermined range, while at the same time, the
temperature detection value and the driving current adjustment
value are stored into the learning table (memory) to be used as
reference data at the time of adjustment later.
[0033] The driving current is controlled based on the data stored
in the learning table during intermittent recording after the
recording operation is suspended. Hence, it is possible to perform
the light power control with high accuracy in a stable manner even
when the recording is performed intermittently and regardless of a
length of intermittent time intervals. In addition, because the
predetermined temperature correction coefficient table is provided,
in the event that the current temperature is out of the range of
the stored temperature detection values and no effective learning
data is available, it is possible to perform the light power
control with high accuracy in a stable manner by using a
predetermined correction coefficient while monitoring the front
emission light from the laser diode 5.
[0034] The invention has been described with reference to the
preferred embodiments thereof. It should be understood by those
skilled in the art that a variety of alterations and modifications
may be made from the embodiments described above. It is therefore
contemplated that the appended claims encompass all such
alterations and modifications.
[0035] This application is based on a Japanese Patent Application
No. 2000-344148 which is hereby incorporated by reference.
* * * * *